Manasara 34.73

34.73

athavā saptāṅgavistāraṃ dvirnavāṃśaṃ karṇāyatam
tadbāhye tu dvibhāgena maṇḍapaṃ paritastathā

Or its width may be seven parts, and its diagonal length twice nine [eighteen] parts; / outside that, all around, there should be a pavilion hall of two parts.